In recent years, developments of household robots such as pet robots have been increasingly advanced, and it is expected that more practical household robots, such as household-chores supporting robots, will be practically used, in the future. Such household robots are required to be coexistent with persons within homes and, therefore, should inevitably come into contact with persons. Accordingly, such household robots are required to be flexible, in view of safety.
To address the aforementioned issue, Patent Document 1 (Japanese Unexamined Patent Publication No. 10-329071) discloses, as a conventional art, a control device which detects a force applied to a robot arm due to the contact between the robot arm and a person and reduces a restoring force for increasing the safety when a large force is applied to the arm, but increases the restoring force for ensuring higher motion accuracy when a very small force is applied to the arm.
Further, Patent Document 2 discloses a control device including a sensor mechanism 515 for detecting the contact portion of a robot 513 which comes into contact with an environment in which an obstruction exists and for detecting the force of the contact, a position orientation determination device 514 for determining the positions and the orientations of a moving mechanism 511 and a manipulator 512, a calculation machine 517 for calculating contact-force avoiding motions of the robot 513 from the contact force and the positions and orientations, and an actuator 516 for driving the moving mechanism 511 and the manipulator 512 according to the result of the calculation by the calculation machine 517, as illustrated in FIG. 11A. In the event that the robot 513 comes into contact with the environment in which the obstruction exists, both the moving mechanism 511 and the manipulator 512 are operated in conjunction with each other to perform avoiding motions.
Further, Patent Document 3 discloses an impedance control device which detects, with a force detection sensor 412, the force applied to a robot 401 having an end effecter 411 by an external environment, then estimates the stiffness coefficient of the external environment in real time and drives and controls the arm 410 of the robot 401 by controlling a motor 413a, as illustrated in FIG. 12.
Patent Document 1: Japanese Unexamined Patent Publication No. 10-329071
Patent Document 2: Japanese Unexamined Patent Publication No. 2005-59161
Patent Document 3: Japanese Unexamined Patent Publication No. 2004-223663